The Group Communication System Enabler (GCSE) is a characteristic of the Third-Generation Partnership Project (3GPP) to allow a group communication service to be provided by a Long Term Evolution (LTE) system so as to enable the LTE network provide the same service for user equipments in a group rapidly and efficiently. A general object of the GCSE is to enable the LTE to provide a public and secured group communication service, and as the LTE technology matures, if an operator can provide a group communication function using the LTE system, then after the LTE system matures, a second-generation or third-generation network may not be maintained any longer, so that the network can transition smoothly to the LTE system.
There are two existing transmission modes of a group communication service:
Multicast transmission where group communication data are transmitted to a number of group members over a shared network resource; and
Uni-cast transmission where group communication data are transmitted to a specific group member over a User Equipment (UE) specific resource
Here multicast transmission is implemented in the LTE system using the existing Multimedia Broadcast/Multicast Service (MBMS) technology, and uni-cast transmission is implemented in the LTE system using the existing uni-cast transmission technology.
The continuity of the group communication service being switched between the two transmission modes needs to be guaranteed.
The network can select the uni-cast transmission mode or the multicast transmission mode to transmit the group communication service, dependent upon the number of subscribers in the group, and the current condition of the network. If the group communication service being transmitted is switched between the uni-cast transmission mode and the multicast transmission mode, then the continuity of the service being switched will be maintained without interrupting the service; otherwise, the experience of the subscribers may be degraded. In an example of a group communication service being interrupted, a UE receives the group communication service in the multicast transmission mode in a current Multicast-Broadcast Single Frequency Network (MBSFN) area, and if the UE moves out of the MBSFN area, then the UE will be unable to further receive the group communication service, so that the group communication service is interrupted. At this time, in order to avoid the group communication service from being interrupted, the UE will be switched from the multicast transmission mode to the uni-cast transmission mode when moving out of the MBSFN area so that the UE further receives the group communication service. Thus in the existing LTE system, uni-cast and multicast transmission is implemented using the existing uni-cast transmission technology and MBMS transmission technology respectively, so the continuity of the group communication service being switched between uni-cast transmission and multicast transmission shall be guaranteed.
In a currently proposed possible solution to guaranteeing the continuity of the service, an eNB configures the terminal with a channel quality threshold in the MBSFN area, and the terminal compares a currently measured quality measurement value of an MBSFN channel with the channel quality measurement threshold, and if the quality measurement value is below the threshold, then the terminal will switch from the multicast transmission mode to the uni-cast transmission mode. However ongoing transmission is not detected for continuity in this solution. Since the group communication service is not dependent upon a geographical position, but can be provided at any position, the performance of the group communication service can be detected through a traditional drive test, for example, by driving along some route. However this detection solution consuming a lot of labors and materials has failed to achieve a good detection effect, and there has been absent in the prior art a solution to processing interruption of the group communication service.